Which tissue is least radiosensitive?

• A. Blood-forming tissue
• B. Gastrointestinal tissue
• C. Cerebrovascular tissue
• D. Muscle tissue

Answer: (C)

Radiosensitivity depends on how actively cells divide and replace themselves. Tissues with rapid cell turnover, like blood-forming tissue and the lining of the GI tract, are highly radiosensitive because radiation readily damages dividing cells and disrupts renewal. In contrast, tissues with slow or minimal cell division—such as muscle and nervous system components—tend to be more resistant to radiation.

Cerebrovascular tissue, part of the brain’s vascular system, contains cells that divide very little under normal conditions, so it shows relatively low sensitivity to radiation compared with the highly proliferative tissues. That makes cerebrovascular tissue the least radiosensitive among the options. Muscle tissue, while fairly resistant, still tends to be more radiosensitive than brain vascular tissue, and blood-forming and gastrointestinal tissues are clearly more sensitive due to their high turnover.